This invention relates to a tenter machine, and more particularly to a low profile tentering system, including chain and rail designs for compact tenter machine applications.
Generally speaking a tenter machine is an open-width fabric-finishing machine in which the selvedges of a woven textile fabric or sheet material are held by a pair of endless traveling carriers in an open width condition while maintaining widthwise tension in the fabric or sheet. For example, tension is maintained in the weft yarns of a fabric. Selvedges are held by a tentering system or tenter frame. Tentering connectors include pin tenters or tentering clips. Other materials having a thin film web can also be tentered. Such tenter machines are used for drying fabric, for heat setting of thermoplastic material, for fixation of chemical finishes and the like.
A typical dryer oven for a compact tenter machine is disclosed in U.S. Pat. No. 4,905,381. The compact dryer oven of this reference is heat efficient and includes a lower housing and an upper housing for providing a short air distribution path and air recycle time. For efficient operation, this dryer oven needs a low-profile tentering system so that proper temperatures can be maintained between the upper and lower housings for fast drying. A clean and efficient tentering system is required to smoothly transport the material through the dryer as it is being held under tension along its selvedges by the tentering system. A low maintenance and low rate of wear tentering system is required for a continuous operation of a tenter machine; typical of a compact tenter machine for drying an endless sheet of material.
A tentering system or tenter frame is used for transporting the sheet material along a longitudinal tentering path. Components of the tentering system include means for driving an endless chain or carrier along the longitudinal path and returning the chain to the start of the longitudinal path. The endless chain forms a closed-loop path and it must be supported along this closed-loop path by tentering rails adjacent the selvedges of the sheet material. The selvedges are held and transported by pins or clip edges of the tentering connectors. A compact tentering system which freely moves the endless chain along the tentering rails with less need for lubrication is most desirable for low wear energy efficient operation and for keeping the sheet material clean.
Typical endless chains forming a closed-loop path for transporting a fabric or sheet material are disclosed in U.S. Pat. Nos. 4,134,189; 4,679,283; 4,877,062; 4,882,820; and 5,265,313. In general, the endless chains are a series of attachment elements or blocks driven by a drive sprocket or wheel for transporting a sheet material under tension along a longitudinal path. Generally speaking, the endless chains of these references require complex bearing assemblies for supporting the chain in a rail assembly. The chains also have a need for lubrication to reduce wear and make the endless chain move freely.
The endless chains are carried by a rail assembly along the closed-loop path. Examples of rail assemblies known in the art are disclosed in U.S. Pat. Nos. 3,469,291; 4,679,283; and 4,882,820. The endless chain moves along or within the rail assembly being supported by the rail assembly itself. In general the rail assemblies of these references require an overall space having a vertical and/or horizontal dimension larger than the space available in the compact tenter machine.
The four U.S. Pat. Nos. 3,469,291; 4,134,189; 4,679,283; and 5,265,313 disclose endless tentering chains with ball bearings that interface with rail assemblies. Each reference discloses an endless chain component comprising a series of anti-friction cylindrical rollers to react the horizontal loads from the sheet material under tension to the rail assemblies. Additional cylindrical rollers or ball bearings are provided for reacting vertical loads from the chain to the rail assemblies, including the weight of the endless chain. The small steel balls within the ball bearings require frequent lubrication to reduce wear on the bearings.
The disclosure of U.S. Pat. No. 4,679,283 illustrates a series of carriers or attachment blocks having cone shaped drivers or roller elements in contact with contacting rails of stationary carrier supports. The attachment blocks are connected together and driven by a drive chain. The stationary carrier supports serve as a tentering rail to include the contact rails on which roller elements move. However, the cone shaped roller elements contact the contact rails over a small area to react horizontal and vertical loads from the carriers to the carrier supports; resulting in a potential for high wear rates.
In U.S. Pat. No. 2,515,399 the ball bearings are also conical to form both a guiding and supporting means for the endless chain. The V-shaped periphery of the ball bearing slides as it rolls along a track of the tentering rail. Once again, the small steel balls within the ball bearings require frequent lubrication to reduce wear on the bearings.
An alternate method of reacting loads from an endless tentering chain to guide rails of a tenter frame is disclosed in U.S. Pat. No. 4,882,820. Slide blocks and slide plates are inserted in the guide rails that interface with the endless chain and support the chain as it moves along the guide rails. The blocks and plates are selected to provide low friction and reduced wear at sliding interfaces. This design depends on a use of materials having a low coefficient of friction during sliding contact so that the endless chain will not become bound by misalignment within the guide rails.
Means for linking the individual components or blocks of the chain together are illustrated in U.S. Pat. Nos. 1,085,538; 4,877,062; and 4,882,820. In U.S. Pat. No. 1,085,538 the individual links have a ball and socket arrangement for connecting the links together. In U.S. Pat. No. 4,877,062 block members are interconnected with a guide means to move the block members along guide rails of the tentering system. U.S. Pat. No. 4,882,820 discloses an endless chain with linking elements comprising slide plates, shoe plates and support plates. These references in general have numerous or complex linking elements linked together.
Tentering clips or pin tenters that grip and support the selvedges of the sheet material are disclosed in U.S. Pat. Nos. 2,515,399; 3,469,291; 4,134,189; and 4,882,820. The tentering clips generally have a vertical dimension which requires a typical compact dryer oven, such as that disclosed above (U.S. Pat. No. 4,905,381), to operate with less efficiency.
The provision of a suitable tentering system having a low-profile rail assembly and an endless carrier remains for compact tenter machines. This is a problem which needs considerable attention. The problem generally exists with providing a low-profile tentering system requiring less lubrication for smooth operation, having low friction load bearing assemblies, requiring less maintenance and having lower wear rates. For example, the low-profile is required to operate a compact dryer oven for drying, heat setting and fixation without relatively large amounts of energy being provided. Tentering clips of the art are also too large to be transported in a low-profile rail assembly. This problem is characterized by the space distribution of the drying energy making it difficult to control the temperature at the faces of the fabric or sheet material. A low-profile endless carrier within a low-profile rail assembly is needed.
Another need exists to define proper use of materials for the rail assemblies and the endless carriers so that bearing assemblies provide interfaces for contacting elements to easily move with respect to one another. A low friction environment is critical for the proper movement of the endless carrier within the rail assemblies, while controlling wear and limiting the use of lubricants to provide a clean environment for the sheet material.
The references do not solve the problems associated with a low-profile tentering system for an energy efficient compact tenter machine. Generally speaking, the references use ball bearings which interface with both horizontal and vertical surfaces within a rail assembly. None of the references disclose an endless tentering chain with bearing assemblies for supporting the bearings to rotate about orthogonal axes to react to both horizontal and vertical loads to the rail assembly. The chains of the art are designed to be made with rigid structural components linked together to form endless chains. The art does not utilize belts or thin metallic straps which can be made into flexible bands for connecting tentering connectors together as an endless belt.
Accordingly, an object of the present invention is to provide a low-profile tentering system or frame for a compact tenter machine and the like.
Another object of the present invention is to provide a tentering system for a tenter machine with attachment blocks having low friction spherical bearing balls that rotate about orthogonal axes for supporting the attachment blocks as they travel on or within rail assemblies.
Yet another object of the present invention is to provide an endless belt or chain interconnecting attachment blocks of a endless carrier having increased flexibility and reliability.
A further object of the invention is to provide connecting guideways of the rail assemblies of a tentering system for guiding an endless carrier having a small angular change in direction along its longitudinal path so that the sheet material is transported from one guideway to the next.
An additional object of the present invention is to provide an endless carrier having improved drive components so that the endless carrier can be driven along a closed-loop path in a horizontal or a vertical plane.
In still another object of the invention the rail assemblies and endless carriers of the tentering system have components made of a material so that rolling and sliding interfaces have low friction and low wear rates.